by Thomas Maresca, Special for USA TODAY

by Thomas Maresca, Special for USA TODAY

BANGKOK - Tens of thousands of protesters in Thailand's capital overran several buildings and cut power to the Finance Ministry on Monday in a stepped-up campaign to topple the government of Prime Minister Yingluck Shinawatra.

Protesters say they want to paralyze the government by forcing civil servants to stop working. They sang, danced and blew whistles in the hallways of government buildings.

The government called the protests an illegal attempt at a coup; opposition spokesperson Akanat Promphan described the protest as a "peaceful sit-in."

Protesters say they are upset because they feel the government is run by Yingluck's brother, former prime minister Thaksin Shinawatra, who was ousted by the military in 2006 and convicted of criminal corruption charges in 2008.

The U.S. Embassy in Thailand issued an advisory Monday, advising American citizens to avoid areas of demonstrations and exercise caution in the vicinity of any large gatherings.

On Sunday, more than 150,000 demonstrators held a rally at Bangkok's Democracy Monument in the largest anti-government gathering seen in Thailand in years. On Monday, protest leader Suthep Thaugsuban led crowds to several spots across Bangkok, snarling traffic.

"Go up to every floor, go into every room, but do not destroy anything," Suthep told the crowd before he entered the Finance Ministry compound and held a meeting in its conference room.

One group cut power at the compound's Budget Bureau in an attempt they said to pressure the agency to stop funding government projects. Akanat Promphan, a former member of parliament who is spokesman for the anti-government opposition, said the rallies garnered "historic turnout."

As evening fell at the darkened Ministry of Finance, protesters continued to arrive as they prepared to settle in for the night in a mostly festive atmosphere. Protest leaders said they would be moving the center of their protests to the ministry compound, but would continue to occupy the Democracy Monument.

Protesters spread out to 13 sites, including the army and air force headquarters as well as several television networks. The scene outside Bangkok's Metropolitan Police Bureau was tense as protesters and riot police outfitted with tear gas and a water cannon faced off across a barricade. Protesters ripped down a barbed wire barricade but did not press further.

Sunai Phasuk, Human Rights Watch senior researcher on Thailand, said the protests were marked by "intolerance and no respect for the diversity of opinions." He singled out for criticism the marches to several Thai television stations, which anti-government protesters accuse of being biased.

"The protesters show very little respect for the work of the media. Part of their activity today was to mobilize tens of thousand of protesters, pressuring TV stations to give them favorable reports and more airtime," he said Monday.

Some worry that fighting could emerge between the anti-government protesters and Thaksin's supporters. The United Front for Democracy Against Dictatorship - known as the red shirts - a political group allied with Thaksin and the Pheu Thai Party, began gathering Sunday at Rajamangala Stadium in Bangkok.

Organizers estimate that the gathering had by Monday grown to at least 50,000 people. In an official statement, they said Monday's occupation of the Ministry of Finance by the anti-government protesters was an act of treason.

The latest wave of political turmoil started with the blanket amnesty bill that was pushed through the lower house of parliament in October. Many saw it as a ploy to allow Thaksin to return from self-imposed exile in Dubai where he fled to avoid a jail term. Bowing to public pressure, the Thai Senate voted the measure down earlier this month.

The protests were the largest since 2010, when 90 people were killed when the red shirts took over parts of Bangkok for weeks before the government, led then by the current opposition, sent the military to crack down.

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